I have a dataset consisting of irregularly-spaced points (x,y,value) that represent an area of ocean that contains some land. I need to interpolate these to a regular grid, ensuring that the interpolation routine does not consider data points that are on the opposite site of a land barrier (e.g. the other side of a peninsular). I understand that this means that I need to insert "breaklines" in the data, and I have polygons of the coastline that I can use for this.

Do any R packages allow for spatial interpolation using breaklines? Ideally I think that natural neighbour interpolation would be the most appropriate for my dataset, but I suspect that the breaklines are more important than the interpolation method.

When posting this question I wasn't sure whether it would be best here or on Stackoverflow. Please feel free to migrate if the community feels that it would be better over there. Thanks!
– FlytoJul 17 '14 at 14:46